Sodalites are known materials, both natural and synthetic. They are generally aluminosilicate framework materials, composed of close-packed truncated octahedral cages, with the unit cell composition M.sub.8 (AlSiO.sub.4).sub.6 X.sub.2, where M is a cation and X is an anion. In some instances the aluminum and silicon are replaced by elements such as gallium, beryllium and germanium. The archetype sodalite is sodium chloro-sodalite. Sodalites are characterized by a lattice structure consisting of a cage of twelve tetrahedral AlO.sub.5.sup.5- or similar units and twelve SiO.sub.4.sup.4- or similar units linked together by oxygen bridges in an alternating pattern to form a truncated octahedron with eight single 6-ring openings and six single 4-rings. This single sodalite cage is diagrammatically represented in FIG. 1 of the accompanying drawings. Typically, the cage has a diameter of 6.6 .ANG. and the diameters of the hexagonal and four-ring openings are 2.2-2.6 .ANG.and 1.5-1.6 .ANG. respectively, according to literature reports. Sodalite cages or .beta.-cages are "tertiary building units" of many zeolites.
Because of the valence difference between aluminum and silicon, the lattice possesses a negative charge equal to the number of aluminum atoms. Large electrostatic potentials are therefore present within the pore system. Resulting from their processes of manufacture, sodalites commonly have an anion trapped in the cage. Thus in sodium chloro-sodalite, a chloride ion occupies the center of each cubo-octahedron. The resulting charge is balanced by four structurally equivalent, tetrahedrally disposed sodium ions, which are coordinated to three framework oxygens of a hexagonal ring and the central anion. The individual .beta.-cages are stacked in eight fold coordination (body centred cubic) so that a given centrally created .beta.-cages shares a hexagonal ring with each of eight adjacent .beta.-cages (an all space filling Federov solid).
A large variety of naturally occurring minerals with diverse compositions are classified as members of the sodalite family. Examples include sodalite Na.sub.8 [(AlO.sub.2).sub.6 (SiO.sub.2).sub.6 9 Cl.sub.2 ; noselite Na.sub.8 [(AlO.sub.2).sub.6 (SiO.sub.2).sub.6 ]SO.sub.4 ; hauynite Na.sub.5-8 Ca.sub.0-2 K.sub.0-1 [(AlO.sub.2).sub.6 (SiO.sub.2).sub.6 ](SO.sub.4).sub.1-2 ; lapis lazuli (Na.sub.2 Ca).sub.4 [(AlO.sub.2).sub.6 (SiO.sub.2).sub.6 ](SO.sub.4,S,Cl.sub.2).sub.2 ; and danalite Fe.sub.8 [(BeO.sub.2).sub.6 (SiO.sub.2).sub.6 ]S.sub.2.
A wide range of anions and cations have been incorporated in synthetic sodalites as encapsulated (so called "packaged") salts. In addition to halides, the anions include hydroxide, cyanide, thiocyanate, perchlorate, bromate, nitrate, azide, sulfite, sulfate, phosphate, manganate, selenite and the like. In addition to alkali metals, the cations include rubidium, silver, tellurium, ammonium, calcium, strontium, lead, zinc, manganese, cadmium etc. Anions such as halides are too large to move through the openings of the sodalite cages and remain trapped therein. Smaller cations can move in and out of the sodalite cages, through the 6-ring openings therein.
The flexibility in sodalite composition allows control not only over lattice charge but also over lattice dimensions. The close packing of .beta.-cages with small openings results in a temperature stable matrix with a uniform pore size distribution that can stabilize small isolated molecules, atoms, ions and radicals which may be air-sensitive or reactive otherwise. Under normal conditions of temperature and pressure the access to the interior of the sodalite framework is restricted for most molecules. It is however possible to carry out chemical reactions within the host-lattice. The trapped species can be studied by appropriate physico-chemical methods.